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New research into Yellowstone National Park geology indicates a more active supervolcano than previously thought while the famous, colossal eruption often cited by scientists that created the 2 million-year-old Huckleberry Ridge deposit was actually two eruptions at least 6,000 years apart. Before the research, conducted by scientists with Washington State University and the Scottish Universities Environmental Research Centre, the “super eruption” was the fourth-largest known to science.

Still, the first eruption qualifies as “super,” as it is one of the largest known to have occurred on Earth and darkened the skies with ash from southern California to the Mississippi River, according to the study, published in the June issue of the Quaternary Geochronology. This compares to the 1980 eruption of Mount St. Helens which produced 1 cubic kilometer of ash. The eruption of Oregon’s Mount Mazama 6,850 years ago produced 116 cubic kilometers of ash.

The new ages for each Huckleberry Ridge eruption reduce the volume of the first event by 12 percent to 2,200 cubic kilometers. A second eruption of 290 cubic kilometers took place more than 6,000 years later, the researchers found.

Scientists studying the Yellowstone volcano used high-precision argon isotope dating to make the new calculations. The radioactive decay rate from potassium 40 to argon 40 serves as a “rock clock” for dating samples and has a precision of .2 percent.

The technique was improved by the WSU/SUERC research team by 1.2 percent allowing for greater temporal resolution.